Undervirilized

Undervirilized is an adjective used in medical and clinical contexts to describe a phenotype with reduced masculinization relative to typical male development. It commonly refers to individuals with XY chromosomes whose external genitalia or secondary sexual characteristics appear less masculine than expected, often due to insufficient androgen exposure or impaired androgen signaling. The term may describe newborns with genital ambiguity or adolescents and adults presenting with incomplete virilization.

Causes are diverse and may include androgen deficiency (for example, impaired testosterone production or Leydig cell dysfunction), androgen insensitivity syndromes (ranging from complete to partial), and enzymatic defects in androgen synthesis such as 5-alpha-reductase deficiency. Less commonly, maternal factors, prenatal environmental exposures, or genetic variations affecting androgen receptors or metabolism can contribute to undervirilization.

Diagnosis typically involves a multidisciplinary assessment, including examination of genitalia and development, karyotype testing when appropriate, and hormonal studies measuring testosterone, dihydrotestosterone, and gonadotropins. Imaging and genetic testing can identify underlying conditions such as androgen receptor mutations or enzyme deficiencies. The assessment aims to determine etiology, degree of virilization, and implications for development and fertility.

Management is individualized and often multidisciplinary, incorporating endocrinology, urology or gynecology, psychology, and social support. Treatment decisions depend on the underlying cause and the individual's age and preferences, and may involve hormone therapy, gender-affirming care, or consideration of surgical options in discussions about genital appearance and function. Ongoing follow-up and counseling are common components of care.